Chapter 4 Diversity Reception in Spread Spectrum

Spread spectrum modulation techniques are mostly employed in wireless communication systems. In order to fully understand spread spectrum communications, we need to have a basic idea on the characteristics of wireless channels. The behavior of a typical mobile wireless channel is considerably more complex than that of an AWGN channel. Besides the thermal noise at the receiver front end (which is modeled by AWGN), there are several other well studied channel impairments [1] in a typical wireless channel: Path Loss which describes the loss in power as the radio signal propagates in space Shadowing which is due to the presence of fixed obstacles in the propagation path of the radio signal Fading which accounts for the combined effect of multiple propagation paths, rapid movements of mobile units (transmitters/receivers) and reflectors. We will give a brief introduction on these three impairments. Our focus is on fading and how spread spectrum techniques can help to combat fading in wireless channels.